I have the same problem with slow response times. For example removing a reminder from a task can take up to 10 seconds. Adding a repeat can take up to 6 seconds.
Initially I though it had something to do with the setup of my 3 year old laptop running on XP.
Two days ago I replaced the laptop with a PC (both are on the same network.)
The PC is running W7 Pro, has a quad core 920 on an Intel Smackover with 12GB RAM and 2 x 1TB 7200 hard drives. I installed the latest version of Firefox - my upload speed = .72Mbps and download = 25.29 Mbps.